KR20040110091A - Method for producing smooth indium-tin-oxide layers on substrates and a substrate coating of indium-tin-oxide - Google Patents

Abstract

PURPOSE: A method and a substrate are provided to manufacture an indium-tin-oxide layer having a low resistance, transparency and conductivity, by using a general sputter source. CONSTITUTION: A method for manufacturing a flat indium-tin-oxide layer on a substrate, comprises a step of sputter-depositing a certain part of an indium-tin-oxide layer in a temperature profile which is controlled to prevent formation of crystallization nucleus; a step of heating the substrate to a temperature higher than a recrystallization temperature of the indium-tin-oxide layer; and a step of sputter-depositing the other part of the indium-tin-oxide layer.

Description

METHOD FOR PRODUCING SMOOTH INDIUM-TIN-OXIDE LAYERS ON SUBSTRATES AND A SUBSTRATE COATING OF INDIUM-TIN-OXIDE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a planar metal oxide layer, and in particular, indium-tin-oxide (hereinafter referred to as Indium-Tin-Oxide) on a substrate used in the manufacture of an organic light-emitting diode (OLED). ITO). The invention also relates to an ITO coated substrate.

In general, organic light-emitting diodes (OLEDs) are fabricated to have a structure that forms a transparent conductive layer on a glass substrate and allows the conductive layer to act as an electrode. Thereafter, various organic layers are deposited on the transparent electrode. These organic layers generally have a very thin thickness in the range of several 10 nm. In order to prevent short circuits or other defects in the circuit which may be caused by spikes or edges on the surface, the transparent electrode must have a very flat surface. The display is finally finished by a generally counter electrode that is metallic and then encapsulated.

Flat ITO layers are often deposited by ion-assisted sputtering or ion plating processes to obtain a flat layer at low temperatures. Among these processes, for example, the Skion process is well known. However, in addition to the sputter source acting as a cathode, ion-assisted sputtering requires an ion source. This means a significant increase in the plant cost of the plant, which automatically leads to an increase in the production cost for the manufacture of such an OLED display. In addition, a disadvantage of the conventional general sputtering process is that it requires an additional mechanical polishing step and thus an additional processing step. This increases the production cost in manufacturing this kind of OLED display as described above.

When a conventional general sputter source is used, especially in a DC magnetron process, the layers are deposited on the substrate at temperatures above the material's recrystallization temperature (about 150 ° C. for ITO) in order to obtain good electrical and optical properties. Is formed. Generally, the substrate is heated to a temperature of 200 ° C. or higher. This heating process is performed because the resistance and transmittance of the ITO layer at low temperatures do not meet the electrical and optical requirements. However, in this method, the growth of the film has a micro crystalline structure, and spikes may occur on the film surface. According to the experimental results, the ITO layer deposited on the substrate at 200 ° C. using a direct current magnetron showed 2.3 nm RMS roughness and 16.1 nm maximum roughness. If it is formed on a thin layer of organic material required for the fabrication of OLEDs, a mechanical polishing process is required to avoid short circuits or other defects caused by spikes or edges on the surface. However, this not only makes the manufacturing of the OLED of the above kind more difficult, but also increases the manufacturing cost.

In order to solve the above problems of the prior art, an object of the present invention is to use a common sputter source such as a direct current magnetron or an RF / DC-pulsed magnetron (RF / DC-pulsed magnetron) process (direct current sputtering or RF / DC sputtering). It is a simple and economical method to provide a method of flatly producing a metal oxide layer such as an ITO layer on a substrate.

This object of the present invention is achieved by the method according to claim 1 and the invention concerning the coated substrate according to claim 6.

1 is a view showing the surface shape of the ITO coated substrate according to an embodiment of the present invention.

2 is a view showing the surface shape of the ITO coated substrate according to another embodiment of the present invention.

The present invention is based on the low temperature deposition layer, in particular in the case of the ITO layer, that crystallization nuclei which remain even if the substrate is subsequently annealed occur only when the thickness of the layer exceeds 70 nm. Thus, according to the present invention, a portion of the final metal oxide layer on the substrate is first sputter deposited in a controlled condition with a temperature profile capable of preventing the formation of crystallization nuclei, and then the substrate is above the recrystallization temperature, In the case of ITO, it is heated to a temperature above 150 ° C., after which the remaining metal oxide layer is formed by sputter deposition.

In the first coating step, part of the ITO layer is preferably formed to a thickness of less than 70 nm, more preferably having a thickness in the range of 25 nm to 50 nm. Here, the coating is preferably formed on a low temperature substrate or at a temperature low temperature substrate of 150 ° C. or less, which is at least the recrystallization temperature of the ITO layer. The coating is preferably formed on a substrate of 100 ° C. or lower, most preferably on a substrate in the range of 15 ° C. to 30 ° C., which is room temperature.

The coated substrate is preferably heated to about 180 ° C. or higher where the rest of the ITO layer is sputter deposited.

Therefore, the present invention provides a flat ITO using a well-known plant technology, such as a conventional general sputter process such as a direct-current magnetron or an RF / DC pulse magnetron process, without additional post processing steps for the production of flat ITO. Create a. In particular, the use of complex, expensive and difficult to control ion-assisted sputtering techniques can be avoided. This is achieved by using temperature dependent growth kinetics of the ITO layer.

The present invention will be described in detail through two examples as shown in FIGS. 1 and 2, and the figure shows an ITO film manufactured according to the present invention.

<Example 1>

The glass substrate is coated with 35 nm of ITO at room temperature by direct current magnetron sputtering using a power density of 2 W / cm 2. After coating, the substrate is heated to 200 ° C. and maintained at this temperature while further coating 105 nm of ITO at a power density of 2 W / cm 2. The film deposited on the substrate had a total thickness of 140 nm, a resistance of 200 μΩcm, a transmittance of 85% for 550 nm wavelength, an effective roughness of 1.0 nm and a maximum roughness of 10.8 nm (FIG. 1).

<Example 2>

The glass substrate is coated with 49 nm of ITO at room temperature by RF / DC pulse magnetron sputtering using a power density of 2.25 W / cm 2. After coating, the substrate is heated to 200 ° C. and maintained at that temperature while 91 nm of ITO is further coated at a power density of 2.25 W / cm 2. The film deposited on the substrate had a total thickness of 140 nm, a resistance of 200 μΩcm, a transmittance of 88% for 550 nm wavelength, an effective roughness of 0.42 nm and a maximum roughness of 4.7 nm (FIG. 2).

By using the method of the present invention, it is possible to produce indium-tin-oxide layers having a very low surface roughness and hence low resistance, transparency and conductivity characterized by no need for mechanical polishing. Indeed, the thin organic material layer needed for the manufacture of the OLED can be produced on the oxide layer without any further work.

Claims (7)

A method of providing a flat metal oxide layer, in particular an Indium Tin Oxide (ITO) layer on a substrate, which produces a transparent conductive ITO layer formed to form an electrode on a glass substrate, in particular an organic light emitting diode As for the preparation of- The ITO layer, First sputter-depositing some ITO layers in a controlled temperature profile to prevent formation of crystallization nuclei; Heating the substrate to a temperature above the recrystallization temperature of the ITO layer; And And sputter depositing the remaining portion of the ITO layer. The method of claim 1, The thickness of the portion of the first sputter deposited ITO layer is less than 70 nm, or preferably in the range of 25 nm to 50 nm. The method according to claim 1 or 2, And said sputter is made by direct current or RF / DC pulse magnetron sputtering. The method according to any one of claims 1 to 3, And some layers by the first sputter deposition are sputter deposited on a low temperature substrate or on a substrate below 150 ° C., preferably at about 100 ° C. or lower. The method according to any one of claims 1 to 4, Wherein said partially coated substrate is heated to a temperature of 150 ° C. or higher, preferably heated to a temperature of 180 ° C. or higher. An Indium Tin Oxide (ITO) coated substrate for the manufacture of an organic light emitting diode, in particular comprising a first amorphous ITO layer of 70 nm or less, according to the method according to claims 1 to 5, ITO coated substrate, characterized in that the ITO layer having a residual thickness is formed on the first amorphous ITO layer. An organic light emitting diode having a flat ITO layer made according to the method of claim 1.